Respiratory protective devices are centuries old and used for the prime objective of protecting the body from airborne pollutants and toxic materials. A relatively new design in the field is the compact, disposable respiratory protective hood. Unlike reusable, bulky and expensive masks having replaceable filters, respiratory protective hoods are designed to be highly compact, effective and adapted for one-time use.
Respiratory protective hoods generally cover the head of a person and seal about the neck perimeter. The hood is constructed of a fluid impermeable material and a flexible, transparent integrated visor is affixed about the front of the hood to permit outward vision by the wearer. Inhaled air is filtered for contaminants and exhaled air is discharged from the hood. Applicant's earlier U.S. Pat. Nos. 6,301,103; 6,371,116; 6,701,925; 6,736,137; 6,817,358; 6,907,878; 7,114,496; and co-pending patent application Ser. Nos. 11/539,960 and 11/551,068 provide substantial background discussions on the state of respiratory protective hood design, all of which are incorporated by reference.
A common use for respiratory protective hoods is deployment in unexpected, emergency situations such as terrorist attacks. By its very nature, terrorist attacks are generally executed without warning to the intended victims. Military, police and civilian personnel have little or no notice prior to an attack. These attacks may include the disbursement of nuclear, biological and/or chemical agents with the intent to kill or injure military and/or civilian populations. Accordingly, it is generally not feasible to carry large, protective devices around at all times. A balance must be struck against the real need to have effective protective gear versus the logistics of carrying the protection around on a day-to-day basis.
A solution has been to vacuum pack the respiratory protective hood in a compact form. Packaged units are sealed until they are needed. The outer packaging is opened and the hood is then unfolded deployed. An important objective in many respiratory hood designs is minimizing the package size and weight. This enhances storage and portability of the device and thus directly relates to the device's availability when it is required.
Yet another consideration is cost of materials and assembly. Bonding rigid structures such as filters to a flexible hood is expensive and complicated. Traditional gas masks have threaded couplings upon which a filter is screwed to form a substantially fluid-tight compression fit against the hood surface. Unfortunately, threads are not always reliable. Threads, if struck by a hard object or dropped may be damaged and thereby form a leak path compromising the protection factor of the apparatus. Furthermore, threads may loosen, again providing a leak path and comprising efficacy. Threaded couplings also add weight and create bulk. Furthermore, funnels for providing the fluid path create even more bulk and increase breathing resistance. An alternative design to the threaded coupling is ultrasonically welding or bonding flanges around a substantially rigid respiratory component. However, these flanges occupy space, add weight and increase the cost of the device. In addition, as flanges increase in size to provide a better mount, the corresponding respiratory component must be reduced in size. Other fittings may include a simple interference fit which may loosen. Yet another fitting may include bayonet fittings. A shortcoming of these attachment methods is that they do not provide the security of a permanent, fluid-tight attachment.
Some respiratory hood designs have attempted to integrate and/or bond flexible filters assemblies directly to the hood. However, none of these designs provide the protection factor and reliability of a filter assembly packed in a substantially rigid housing.
There is a long-felt but unfulfilled need in the art for a flexible respiratory protective hood that has substantially rigid respiratory components such as filters bonded directly to the hood material without the bulk, expensive or other comprises associated with threaded couplings or flanges.